He had returned to right a few wrongs. Lukaku, as he admitted himself, had made a massive mistake in leaving Inter for Chelsea in the summer of 2021 and he was thrilled to get the chance to make amends.
The club were delighted to have him back, too. Indeed, it looked like another Beppe Marotta masterstroke: re-signing a player on loan for €8 million (£7m/$9m) a year after selling him for £97.5 million ($117m).
In that sense, Lukaku was a low-risk gamble well worth taking. And yet it's still managed to backfire badly.
The highest-paid striker in Serie A has managed just six goals in all competitions, with his campaign characterised by one shocking miss after another.
Indeed, after somehow contriving to hit the crossbar with a header from two yards out in Friday's 1-1 draw at Salernitana, Lukaku felt compelled to apologise afterwards to Inter's travelling fans.
It was a touching gesture, an admirable acknowledgement from a very honest character that he is not doing enough for his struggling side right now, and it was very much appreciated by the supporters.
"Always facing up to things, it doesn't matter if things go well or badly, what counts is taking responsibility," the Curva Nord wrote on Instagram.
While Lukaku has gone some way towards rebuilding a relationship he ended in brutal fashion by leaving for Chelsea without even a word of explanation, it now seems highly unlikely that he will still be at Inter next season.